Throughout the art is disclosed numerous controlled release devices for administering medication such as drugs, as well as food supplements such as vitamins to animals such as livestock (e.g., horses, cattle, pigs, etc.). Heretofore, said medication was primarily administered to animals via feed and syringe methods.
Representative controlled delivery devices disclosed in the art are indicated below:
1. U.S. Pat. No. 4,200,098 (1980)--An osmotic system is disclosed for dispensing a beneficial agent. The system comprises (1) a first wall of a semipermeable material that surrounds a compartment containing a drug formulation, and has a passageway through the wall for releasing agent from the compartment, (2) a second wall positioned distant from the first wall, said second wall a microporous or hydrogel material that extends around the first wall, and (3) a distribution zone interposed between the first and second wall and initially housing a compound soluble in an external fluid that enters the system.
2. U.S. Pat. No. 4,077,407 (1978)--discloses an osmotic device for delivering an active agent. The device is comprised of a wall surrounding a compartment and has a passageway through the wall for releasing the agent. The wall is formed of a multiplicity of materials comprising a material permeable to an external fluid and substantially impermeable to agent and at least one additional material selected from a material that imparts stability to the wall, enhances the permeability of the wall to fluids, or aids in forming the wall. The compartment comprises an active agent that exhibits an osmotic pressure gradient against an external fluid, or the agent is mixed with an osmotically effective compound that exhibits an osmotic pressure gradient against the fluid. Agent is released from the device by fluid being imbibed through the wall into the compartment at a rate controlled by the permeability of the wall and the osmotic pressure gradient across the wall, to produce a solution containing agent that is released through the passageway at a controlled and continuous rate over a prolonged period of time.
3. U.S. Pat. No. 4,160,020 (1979)--An osmotic device is disclosed for delivering an active agent. The device comprises a wall surrounding a compartment with a passageway through the wall for releasing the agent. The wall comprises a material permeable to an external fluid and substantially impermeable to agent and at least one additional material independently selected from materials that impart stability to the wall, enhance the permeability of the wall to fluids, or aid in forming the wall. The compartment contains an agent that exhibits an osmotic pressure gradient across the wall against an external fluid, or the agent is mixed with an osmotically effective compound that exhibits an osmotic pressure gradient against the fluid. Agent is released from the device by fluid being imbided through the wall into the compartment at a rate controlled by the permeability of the wall and the osmotic pressure gradient across the wall, thereby producing a solution containing agent that is released through the passageway at a controlled rate over time.
4. U.S. Pat. No. 4,327,725 (1982)--An osmotic device is disclosed comprising a semipermeable wall surrounding a compartment housing an agent that is insoluble to very soluble in aqueous and biological fluids, and a layer of a fluid swellable, hydrogel. A passageway in the wall connects the agent with the exterior of the device.